Effects Of Land Use Change On Soil And Soil Aggregates In Bond-organic Carbon

In this study,select the same conditions of the natural forests (Altingia gracilipes),plantation(Cunninghamia lanceolata and Schima and seal silviculture),orchard (citrus orchard and teagarden),slope farmland which located in the subtropical regions as the research objects,throughresearching the land use changes to influence on soil,aggregates speciation organic carbon,and therelationship between speciation organic carbon and soil carbon to reveal the protection ofmountain soils carbon sequestration aggregates and chemical bonding mechanism insubtropical,through comparing dry sieving with wet sieving to study the differences between twokinds of speciation organic carbon to understand the applicability of dry and wet sieving methodin soil aggregates in the subtropical regions,analysis soil aggregates easily oxidized organiccarbon.Mineral protected organic carbon and chemical recalcitranced organic carbon madecontribution to the total carbon and the relationship between land use changes,provide ideas forthe adjustment of mountain land used in scientific way,and enhance the capacity of carbon sink insub-tropical area in our Country,so as to further illustrate the impact of land use change on soilorganic carbon sequestration,these are all of great significance to promote the ecological cycle forachieving sustainable use of the northern Fujian land. Mainly the following conclusions:1After natural forest conversion to plantation,orchard and slope farmland,the whole soilorganic carbon decreased in some extent, the Ca-SOC decline more than Fe(Al)-SOC,but thedescender was not significant, and the content of soil organic carbon in0-10cm soil horizon wasmore than10-20cm. For the internal aggregates speciation organic carbon,the land use changeshave an effect on them,after natural forest converted to other used land, the decline of theFe(Al)-SOC was significantly higher than the Ca-SOC,especially in natural forest conversion tothe sloping land,the loss rate of the internal aggregates speciation organic carbon is up to97.18%,the difference may be due to the Fe(Al)-SOC is mainly loose state,Ca-SOC is mainly steadystate,therefore,land use change in the pattern,so that a greater degree of Fe(Al)-SOC declinedorganic carbon knot steady state,therefore,the change in land use make a greater descender inFe(Al)-SOC.The different size of Aggregates,speciation organic carbon make the greatestdescender of internal aggregates speciation organic carbon in the <0.25mm, which means thatSOC in soil aggregates made the greatest contribution to the total carbon.2Two different aggregates screening method of dry sieving and wet sieving make differenceinfluence on two different kinds of particle size aggregate speciation organic carbon.It causedsome differences in Aggregates Ca-SOC content, but was not significant.For Fe(Al)-SOC,interms of the wet sieving and dry sieving,the wet sieving resulting in a reduction of its content. Twoscreening methods make the two very different results,may be attribute to their inconsistencthermal stability, and inconsistent with the bond of humic substances.3After natural forest conversion for other use of land, the content of LOC in soil aggregates have undergone a significant loss,especially reclamation for the arable land,the loss of LOCreserves up to about87%,it is suggest that LOC is more sensitive to the changes of land use. In thesame way use of different soil particle size aggregates,the content of LOC in micro-reunion ismore than large aggregates. So that,in the process of land management,should pay attention toreduce the interference of micro-aggregates in order to reduce the loss of organic carbon.4The conversion of forest land to the garden or sloping land,appeared a large extentreduction in the particle size of soil aggregates,mineral protected organic carbon,especiallyreclaimed to sloping land,the rate of loss is up to97%. Similarly,the content of chemicalrecalcitranced organic carbon is relatively large loss,but the magnitude is less than the mineralprotected organic carbon,the maximum loss amount is up to about70%. in the same use patternsof different size aggregates mineral protection of state,and chemical recalcitranced organic carbonare both assume the micro-aggregates are greater than large aggregates (except for Cunninghamialanceolata).5Under different land use pattern,there are very significant correlation between bond-organiccarbon and total carbon of soil aggregates,but varied in soil.In natural forest and plantation,thereare highly significant positive correlation between the Ca-SOC and SOC,and no correlation inorchard.There is no correlation between Fe(Al)-SOC and SOC in each soil of different land usepattern.Therefore,bounded organic carbon in soil aggregates can be used as one of the indicatorsthat characterize the total carbon content.Sililarly,the content of LOC significantly related to thecontent of SOC,the increasing in SOC will lead to the rising of the content of LOC,LOC in soilaggregates can be used as a sensitive indicator reflects the land use change.Mineral protectedorganic carbon and chemical recalcitranced organic carbon were not significantly correlated toSOC in different size of soil aggregates.